1. Field of the Invention
The present invention relates to a multi-phase reactor capable of obtaining a constant inductance for each phase.
2. Description of the Related Art
For example, a three-phase reactor has been conventionally used in an industrial robot, a machine tool, and so on in order to reduce a failure of an inverter and to improve a power factor by being disposed between a power-supply side (primary side) and the inverter or between a load side, such as a motor, (secondary side) and the inverter.
Specifically, a three-phase reactor is disposed on a primary side of an inverter to improve a power factor (for harmonics countermeasure) and to reduce a surge from a power supply. Alternatively, a three-phase reactor is disposed on a secondary side of an inverter to reduce a noise of a motor during operation of an inverter and to take a countermeasure against a surge. A description is given herein of mostly a three-phase reactor as an example. However, applications of the present invention are not limited to a three-phase reactor. The present invention may be a multi-phase reactor other than a three-phase reactor.
By the way, various multi-phase reactors have been conventionally proposed. For example, a three-phase reactor generally includes three cores (iron cores) and three windings (coils) wound around the cores. For example, Japanese Laid-Open Patent Publication No. H02(1990)-203507 (Patent Literature 1) discloses a three-phase reactor including three windings arranged in parallel.
Further, International Laid-open Patent Publication No. WO 2014/033830 (Patent Literature 2) discloses an arrangement of central axes of a plurality of respective windings around a central axis of a three-phase reactor. This arrangement is considered as being obtained by arranging the three winding portions in Patent Literature 1 at vertex positions of an equilateral triangle, rather than arranging the three winding portions in a row.
Further, Japanese Laid-open Patent Publication No. 2008-177500 (Patent Literature 3) discloses a variable reactor capable of varying a reactor which includes six linear magnetic cores arranged in a radial direction, coupling magnetic cores coupling the linear magnetic cores, and windings wound around the linear magnetic cores and the coupling magnetic cores. In addition, no gap portion is provided in order to make a reactance variable.
For example, a conventional three-phase reactor generally includes three cores (winding cores) around which windings are respectively wound, and which are arranged in a row between an upper core and a lower core, with predetermined gaps provided with respect to the lower core. Such a three-phase reactor is line-symmetric with respect to a central line of, for example, a center winding core.
However, a line-symmetric three-phase reactor formed of three winding cores undergoes the imbalance between a center winding core (winding) and winding cores at opposite ends. Thus, this is a problem in that it is difficult to set a constant value of inductance for three phases, namely, R-phase, S-phase, and T-phase.
In light of the above-described problem in the related art, the present invention aims to provide a multi-phase reactor capable of setting a constant value of inductance for each phase.